256 



DR. A. RANSOME ON GRAPHICAL REPRESENTATION 



be on the usually received hypothesis, that the ribs are 

 simply rigid bars moving upon the support of their costo- 

 vertebral joints. 



It is not difficult to construct the curve which ought to 

 be described by the end of the rib on this hypothesis. The 

 average chord-length of the third rib is known ; and the 

 expiratory and inspiratory angles made by the plane of the 

 rib with the vertical can easily be ascertained. Fig. 5 a 

 gives the curve produced with a radius of 6 inches and an 

 initial angle of 60°, conditions resembling those of the 

 chest from which figs. 1 and 2 were taken. 



Again, another, more direct means of ascertaining the 

 curve formed by the end of the rib in its rise and fall may 

 be taken ; and fig. 5 b represents the actual motion of the 



fifth rib in a dead male subject, in whom the fourth and 

 fifth intercostal spaces had been divided, and the costo- 

 sternal attachment released, so as to permit of free move- 

 ment at its vertebral articulation. The rib was then 

 simply raised and depressed, whilst the button of the 

 stethograph rested upon it. 



In fig. 5 c some inward pressure was made upon it 

 during its descent, and gradually removed during its 

 ascent. 



Now the curve constructed by the simple rise and fall 



